Cmp apparatus and method

ABSTRACT

A CMP apparatus includes an enclosure; a platen disposed within the enclosure, and a carrier for holding and rotating a wafer. The platen consists of a central, circular-shaped segment and a peripheral, annular-shaped segment with a gap formed therebetween. A first polishing pad is mounted on the central, circular-shaped segment. A second polishing pad is mounted on the peripheral, annular-shaped segment. In polishing, the carrier rotates between the first and second polishing pads, such that an annular edge region of the wafer is in direct contact with the second polishing pad.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of chemical mechanical polishing or chemical mechanical planarization (CMP) techniques. More particularly, the present invention relates to an improved CMP apparatus and a CMP method capable of precisely controlling the polishing uniformity in the CMP process.

2. Description of the Prior Art

As known in the art, mechanical polishing or chemical mechanical planarization (CMP) is essential to the semiconductor fabrication to achieve a high degree of planarity on the surface of a semiconductor wafer. In a CMP process, the wafer is typically pressed against a rotating polishing pad. The wafer may rotate and oscillate over the surface of the polishing pad covered with slurry to improve polishing effectiveness.

FIG. 1 illustrates a conventional CMP polishing unit. As shown in FIG. 1, the CMP polishing unit 30 may comprise a platen 300 connected to a shaft 301 for rotating the platen 300 about its central axis during polishing. A polishing pad 310 is mounted on the platen 300. A wafer 322 is held and rotated by a carrier 320. In polishing, slurry is sprayed onto the polishing pad 310 by a slurry feeding device 330. The rotating wafer 322 is pressed against the polishing pad 310 by the carrier 320 to cause relative movement between the polishing surface of the polishing pad 310 and the wafer 322, thereby producing a combined mechanical and chemical effect on the surface of the wafer. The polishing pad 310 is typically made several times the diameter of the wafer 322. The wafer 322 is kept off-center on the rotating polishing pad 310 during the polishing process.

One problem associated with the conventional CMP techniques is the difficulty in controlling polishing rates at different locations on a wafer surface. Since the polishing rate applied to a wafer surface is generally proportional to the relative rotational velocity of the polishing pad, the polishing rate at a specific point on the wafer surface depends on the distance from the axis of rotation. It is desirable to control the uniformity in the CMP process because it enables the subsequent use of a high-resolution lithographic process to fabricate the next level circuit. The accuracy of a high resolution lithographic process can be achieved only when the process is carried out on a substantially flat surface.

SUMMARY OF THE INVENTION

It is one object of the present invention to provide an improved CMP apparatus in order to solve the above-described problems.

To these ends, according to one aspect of the present invention, there is provided a CMP apparatus comprising: an enclosure; a platen disposed within the enclosure, wherein the platen consists of a central, circular-shaped segment and a peripheral, annular-shaped segment encircling the central, circular-shaped segment with a gap therebetween; a carrier for holding and rotating a wafer; a first polishing pad mounted on the central, circular-shaped segment; and a second polishing pad mounted on the peripheral, annular-shaped segment. A first nozzle is provided for supplying a first slurry onto the first polishing pad. A second nozzle is provided for supplying a second slurry onto the second polishing pad. The first slurry and the second slurry may be supplied at different flow rates.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a schematic diagram showing a conventional CMP polishing unit;

FIG. 2 is a schematic, cross-sectional diagram illustrating a CMP apparatus in accordance with one embodiment of this invention; and

FIG. 3 is a schematic plan view showing the relative position of the polished wafer and the polishing pads in accordance with one embodiment of this invention.

It should be noted that all the figures are diagrammatic. Relative dimensions and proportions of parts of the drawings have been shown exaggerated or reduced in size, for the sake of clarity and convenience in the drawings. The same reference signs are generally used to refer to corresponding or similar features in modified and different embodiments.

DETAILED DESCRIPTION

In the following description, numerous specific details are given to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the invention may be practiced without these specific details. In order to avoid obscuring the present invention, some well-known system configurations and process steps are not disclosed in detail.

Likewise, the drawings showing embodiments of the apparatus are semi-diagrammatic and not to scale and, particularly, some of the dimensions are for the clarity of presentation and are shown exaggerated in the figures. Also, where multiple embodiments are disclosed and described having some features in common, for clarity and ease of illustration and description thereof like or similar features one to another will ordinarily be described with like reference numerals.

FIG. 2 is a schematic, cross-sectional diagram illustrating a CMP apparatus in accordance with one embodiment of this invention. As shown in FIG. 2, the CMP apparatus 10 comprises an enclosure 100, a platen 110 disposed within the enclosure 100, and a carrier 220 for holding and rotating a wafer 222. The platen 110 is connected to a shaft 101 for rotating the platen 110 about its central axis during polishing. According to one embodiment of the invention, the platen 110 consists of a central, circular-shaped segment 110 a and a peripheral, annular-shaped segment 110 b encircling the central, circular-shaped segment 110 a with a gap 113 therebetween. The central, circular-shaped segment 110 a and the peripheral, annular-shaped segment 110 b are concentric. According to the embodiment of this invention, the gap 113 has a width d of about 0.5-5 mm.

A first polishing pad 112 a is mounted on the central, circular-shaped segment 110 a. A second polishing pad 112 b is mounted on the peripheral, annular-shaped segment 110 b. The material used for the first polishing pad 112 a and the material used for the second polishing pad 112 b may be the same or different. A first slurry S1 is provided onto the first polishing pad 112 a via a first nozzle 230 a. A second slurry S2 is provided onto the second polishing pad 112 b via a second nozzle 230 b. The flow rate and the concentration settings of the first slurry S1 and the flow rate and the concentration settings of the second slurry S2 may be the same or different.

FIG. 3 is a schematic plan view showing the relative position of the polished wafer and the polishing pads in accordance with one embodiment of this invention. As shown in FIG. 3, the central, circular-shaped segment 110 a and the peripheral, annular-shaped segment 110 b rotate in the same direction 150, for example, both in counter-clockwise direction, but at different rotation speeds. According to the embodiment of this invention, the rotation speed of the peripheral, annular-shaped segment 110 b is slower than that of the central, circular-shaped segment 110 a. A differential gear (not shown) may be installed to provide such different rotation speeds.

In polishing, the rotating wafer 222, which is rotated, for example, in a direction 250 opposite to the direction 150, is pressed against the first and second polishing pads 112 a and 112 b by the carrier 220 to cause relative movement between the polishing surfaces of the first and second polishing pads 112 a and 112 b and the wafer 222. According to the embodiment of this invention, the location of the carrier 220 is adjustable along the direction 260. According to the embodiment of this invention, the carrier 220 rotates between the first and second polishing pads 112 a and 112 b, such that an annular edge region E of the wafer 222 is in direct contact with the second polishing pad 112 b. Preferably, the surface area of the annular edge region E is about one-third of the total surface area of the wafer 222.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. 

1. A CMP apparatus, comprising: an enclosure; a platen disposed within the enclosure, wherein the platen consists of a central, circular-shaped segment and a peripheral, annular-shaped segment encircling the central, circular-shaped segment with a gap therebetween; a carrier for holding and rotating a wafer; a first polishing pad mounted on the central, circular-shaped segment; and a second polishing pad mounted on the peripheral, annular-shaped segment.
 2. The CMP apparatus according to claim 1 further comprising: a first nozzle for supplying a first slurry onto the first polishing pad; and a second nozzle for supplying a second slurry onto the second polishing pad.
 3. The CMP apparatus according to claim 2 wherein the first slurry and the second slurry are supplied at different flow rates.
 4. The CMP apparatus according to claim 2 wherein the first slurry and the second slurry have different concentration settings.
 5. The CMP apparatus according to claim 1 wherein the gap has a width d of about 0.5-5 mm.
 6. The CMP apparatus according to claim 1 wherein the central, circular-shaped segment and the peripheral, annular-shaped segment rotate in the same direction.
 7. The CMP apparatus according to claim 1 wherein the central, circular-shaped segment and the peripheral, annular-shaped segment rotate at different rotation speeds.
 8. The CMP apparatus according to claim 7 wherein the rotation speed of the peripheral, annular-shaped segment is slower than that of the central, circular-shaped segment.
 9. The CMP apparatus according to claim 1 wherein in polishing the carrier rotates between the first and second polishing pads, such that an annular edge region of the wafer is in direct contact with the second polishing pad.
 10. The CMP apparatus according to claim 9 wherein a surface area of the annular edge region is about one-third of a total surface area of the wafer. 